Apparatus and method for detecting live cells with an integrated filter and growth detection device

ABSTRACT

A device for processing fluids includes a filter to capture a cell sample. The filter has a physical barrier to isolate the cell sample on the filter. Growth detection circuitry is associated with the filter. The growth detection circuitry identifies, through electrical measurements, a cell growth rate and hence the presence of live cells associated with the cell sample.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/467,086, entitled, “A & M For Detecting BacterialContaminants In A MEM Device With Integrated Filters And BacterialGrowth Detection Circuitry,” filed Apr. 30, 2003.

BRIEF DESCRIPTION OF THE INVENTION

[0002] This invention relates generally to the detection of live cells.More particularly, this invention relates to a method and structure fordetecting live cells with a micro-fabricated device with an integratedfilter and growth detection circuitry.

BACKGROUND OF THE INVENTION

[0003] Micro-fluidics has found increasing use in a wide variety ofbiomedical applications, including detection and characterization ofbiological entities. The devices used for such applications are broadlyreferred to as “biochips”. The term biochip has been used in variouscontexts, but can be generally defined as a micro or nano-fabricateddevice that is used for processing (e.g., delivery and analysis) ofbiological entities (e.g., molecules, cells, etc.). This inventionrelates to the processing of biological entities in the form of cells.As used herein, the term cell broadly refers to any microscopicorganism, including bacteria, spores, molds, yeast, plant cells, andanimal cells. The invention will be primarily disclosed through theexample of bacteria detection. However, it should be appreciated thatthe invention is generally applicable to the detection of any type ofcell.

[0004] Biochips based on the impedimetric detection of biologicalbinding events or the amperometric detection of enzymatic reactionsexist. Impedimetric detection works by measuring impedance changesproduced by the binding of target molecules to receptors (antibodies,for example) immobilized on the surface of microelectrodes. Amperometricdevices measure the current generated by electrochemical reactions atthe surface of microelectrodes, which are commonly coated with enzymes.Both of these methods can be very sensitive, but preparation of thesurfaces of the electrodes (immobilization of antibodies or enzymes) isa complex and sometimes unreliable process, that can be prone to driftand tends to be very sensitive to noise produced by the multitude ofspecies present in real samples (bodily fluids, food, soil, etc.).

[0005] A specific example of use of biochips is for the detection oflive bacteria and cells from a sample. The very important requirementfor the micro-fabricated, impedance-based detection system for thisapplication is the ability to concentrate the small numbers of cellspresent in the sample being analyzed into the micro-fabricated volumewhere detection is performed. One prior art approach is to usedielectrophoresis (DEP) to capture immunobeads (microscopic beads coatedwith charged molecules or antibodies) carrying the cells of interestinside the detection chamber. There are two reasons to use beads. First,the dielectrophoretic force is higher in magnitude on beads in thegrowth media when compared to the force on cells in the media. Second,the beads could also be used for specific capture of cells.

[0006] A key shortcoming associated with existing techniques usingbiochips for the detection of cells and their growth is that thefiltering steps and growth detection steps are separate operationsperformed on different devices. Various processing operations arecurrently required to bridge these different operations. For example, afiltering operation performed on the original sample volume of up to ahalf-liter may use a filter membrane to capture a sample. The filtermembrane is then manually moved to a growth area to grow the cellstrapped on the membrane. Thus, current filter isolation and transportoperations are time consuming and are prone to a variety of errors. Inaddition, prior art approaches cannot be integrated in an automated wayin manufacturing processes where testing of various fluids is performed.It would be highly desirable to eliminate these problems through tightlycoupled filtering and cell growth detection operations.

[0007] Current methods of bacteria detection almost always involve agrowth step wherein the microorganisms are cultured to increase theirnumbers by several orders of magnitude. Depending on the type ofbacteria, this amplification by means of extended growth makesconventional detection methods extremely lengthy, taking anywhere from 2to 7 days. It would be highly desirable to significantly reduce thisamplification stage processing time.

[0008] In sum, it would be highly desirable to reduce the amount of timerequired for cell amplification. Finally, it would be highly desirableto simplify fluidic processing through integrated filtering and cellgrowth operations.

SUMMARY OF THE INVENTION

[0009] The invention includes a device for processing fluids. The deviceincludes a filter to capture a cell sample. The filter has a physicalbarrier to isolate the sample on the filter. Growth detection circuitryis associated with the filter. The growth detection circuitryelectrically measures a growth rate associated with the sample.

[0010] The invention also includes a method of processing fluids. A cellsample is captured within a fluid with a physical barrier. The sample isheated. A growth rate signal associated with the cell sample is thenmeasured. These operations are performed on an integrated device.

[0011] The invention integrates filter and recovery operations in asingle device. The invention enables the electrical detection of livecells in 2-4 hours, as opposed to the prior art requirement of 2-7 days.Most systems available in the market today, based on impedancemicrobiology or other techniques, have a detection threshold of 10⁶cells. The disclosed system has a theoretical sensitivity of 1-10 cells.

BRIEF DESCRIPTION OF THE FIGURES

[0012] The invention is more fully appreciated in connection with thefollowing detailed description taken in conjunction with theaccompanying drawings, in which:

[0013]FIG. 1 illustrates an integrated filter and growth detector of theinvention as used with a fluidic control device and a computer.

[0014]FIG. 2 is a cross-sectional view of the integrated filter andgrowth detector of the invention coupled to a fluidic control device.

[0015]FIG. 3 is a top view of an integrated filter and growth detectorconfigured in accordance with an embodiment of the invention.

[0016]FIG. 4 is a cross-section view of the integrated filter and growthdetector of FIG. 3 taken along the line 4-4.

[0017]FIG. 5 is a cross-sectional view of an alternate embodiment of anintegrated filter and growth detector of the invention.

[0018]FIG. 6 is a cross-sectional view of another embodiment of anintegrated filter and growth detector configured in accordance with anembodiment of the invention.

[0019]FIG. 7 is a cross-sectional view of another embodiment of anintegrated filter and growth detector configured in accordance with anembodiment of the invention.

[0020]FIG. 8 is a cross-sectional view of another embodiment of anintegrated filter and growth detector configured in accordance with anembodiment of the invention.

[0021]FIG. 9 is a cross-sectional view of a multi-chamber integratedfilter and growth detector configured in accordance with an embodimentof the invention.

[0022]FIG. 10 is a top view of another embodiment of an integratedfilter and growth detector configured in accordance with an embodimentof the invention.

[0023] Like reference numerals refer to corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0024]FIG. 1 illustrates an integrated filter and growth detector 20 ofthe invention that may be used with other components shown in thefigure. As will be illustrated, the detector 20 includes one or moremicron-scale or nano-scale physical barriers that operate as filters toisolate and capture a cell sample from a fluid. The detector 20 furtherincludes integrated growth detection circuitry to electrically measure agrowth rate associated with the captured sample. The integrated filterand growth detector 20 may be a stand-alone device or it may bepositioned within a carrier package 22. In either embodiment, the deviceis adapted to facilitate handling and interfacing with other physicaldevices. By way of example, the device may be a plastic package withelectrical leads, means to control and maintain temperature for optimalcell growth, and fluid ports. The device may be disposable or reusable.

[0025]FIG. 1 further illustrates a fluidic control device 24. Thefluidic control device 24 is configured to process fluids and tointerface with the integrated filter and growth detector 20, as shownbelow.

[0026]FIG. 1 also illustrates a signal processing and display device(e.g., a computer) 26. In one embodiment, the device 26 includes a setof input and output devices 28 that provide electrical interfaces to thefluidic control device 24 and the integrated filter and growth detector20. The input and output devices 28 operate under the control of acentral processing unit 30, which is linked to the input and outputdevice 28 over a bus 32. A memory 34 is also attached to the bus 32. Thememory 34 stores a set of executable programs. In this example, thememory 34 stores an executable program in the form of a fluidic controlmodule 36. The fluidic control module includes executable instructionsto control the operation of the fluidic control device 24. Controlsignals are passed to the fluidic control device 24 through input andoutput devices 28.

[0027] The memory 34 also stores a signal acquisition and analysismodule 38. The signal acquisition and analysis module 38 includes a setof executable instructions to process growth rate signals generated bythe integrated filter and growth detector 20. In addition, the signalacquisition and analysis module 38 includes executable instructions tocontrol processing on the detector 20. For example, the module 38controls heating operations performed on the detector 20. In oneinstance, the module 38 processes an initial device temperature, selectsa temperature value, applies a control signal to generate thetemperature value on the device, and then monitors the device tomaintain the temperature value.

[0028]FIG. 2 is a cross-sectional view of a fluidic control device 24and an integrated filter and growth detector 20 that may be used inaccordance with the invention. The fluidic control device 24, in thisexample, includes a sample reservoir 40, a de-ionized or distilled waterreservoir 42, a growth media reservoir 44, and a waste reservoir 46. Apump 49 is used to transport the fluids, while valves 48 are used tocontrol the fluid flow.

[0029] As shown in FIG. 2, the integrated filter and growth detector 20is adapted to interface with the fluidic control device 24. In thisembodiment, the detector 20 includes a filter end 50 and a growthdetector end 52 connected by a channel 54. The filter end 50 has a firstinput port 60, a second input port 62, and an output port 64.

[0030]FIG. 3 is a top view of an integrated filter and growth detector20 configured in accordance with an embodiment of the invention. Thedetector 20 includes a filter end 50 and a growth detector end 52connected by a channel 54. The filter end 50 includes a filter 70, whilethe growth detector end 52 includes a base 80. The base 80 (e.g., aprinted circuit board) has a metal heater with associated temperaturecontrol circuitry (e.g., a sensor). The base 80 also has a separate setof metal electrodes for sensing bacterial growth rate signals generatedin measurement chamber 82. The bacterial growth rate signals are routedto an external device, such as computer 26 through electrodes 84.

[0031]FIG. 3 illustrates an input port 60, which may be used to inject afluidic sample of interest, such as growth media. FIG. 3 alsoillustrates an input port 62, which may be used for pumping operationsand an output port 64, which may be used to pass waste fluids. A channel90 links input port 62 to the measurement chamber 82, while anotherchannel 92 links the output port 64 to the measurement chamber 82.

[0032] In this example, the detector 20 is a plastic cartridge fordisposable use. The filter 70 may be formed within the plastic cartridgebody. The filter may be polycarbonate or another plastic material. Thegrowth detector end 52 may include a silicon-fabricated device formingthe measurement chamber 82 and required electrical leads. FIG. 4 is across-sectional view taken along the line 4-4 of FIG. 3.

[0033]FIG. 4 illustrates the filter end 50 and growth detector end 52 ofthe device. The filter end 50 includes an input port 60, an input port62, and an output port 64. FIG. 4 illustrates a seal 60 and a threadedmember 102 to connect to the device 20. The figure also illustratesfilter 70, plus an additional filter 71. The figure also illustrates thepreviously discussed channel 54, which has an outlet 110 to deliver afluid to measurement chamber 82. In this example, the diameter of theoutlet 110 is 150 μm. The growth detector end 52 also includes a metalheater 112, a silicon substrate 114 and a glass or quartz cover 114.These components may be mounted on a printed circuit board. Standardsemiconductor processing techniques are used to form a cavity in thesilicon substrate 114, which serves to operate as a measurement chamber.Similarly, standard semiconductor processing techniques are used to forma heater, a temperature sensor, leads and electrodes to measure a growthrate signal.

[0034] In one instance, the device of FIGS. 3-4 is used to concentrate a100 ml sample, recover the bacteria from the filter 70 and move thebacteria to the measurement chamber 82. The bacteria may be furtherconcentrated in the measurement chamber 82 using a combination ofdielectrophoresis, a mechanical filter, or anti-bodies/proteins. Thebacteria may also be provided with growth media to facilitate rapidgrowth. While the bacteria are heated and grown, the growth is detectedelectronically. In one embodiment, impedance changes over time are usedto detect the growth.

[0035]FIG. 5 illustrates an alternate embodiment of the integratedfilter and growth detector of the invention. The detector 120 of FIG. 5is formed from a stack of semiconductor wafers, including a first wafer130, a second wafer 132, and a third wafer 134. A first mechanicalfilter 140 is formed in the first wafer 130. The first mechanical filter140 comprises a set of apertures 142 etched into the first wafer 130.While only a small number of apertures are shown in FIG. 5, it should beappreciated that there will typically be a large number of aperturesetched into the wafer. The first mechanical filter 140 is positioned ata first input port 144 formed by tube 146. The first wafer 130 alsoincludes a first output port 148, surrounded by a tube 150.

[0036]FIG. 5 also includes a second wafer 132. The second wafer 132includes a second mechanical filter 160. The apertures of the secondmechanical filter 160 are smaller than those formed in the firstmechanical filter 142. By way of example, the first mechanical filter142 has pore sizes between approximately 2 and 12 μm, preferably betweenapproximately 4 and 8 μm, to trap particles larger than bacteria. Thesecond mechanical filter 160 has pore sizes of approximately 0.2 μm orless to trap bacteria. The thickness of each filter and the percent areaof pores is a function of the desired flow rate and the pressure thatthe membrane can withstand. The second wafer 132 also defines a channel162. Electrodes 164 are formed in the channel 162 for impedancemeasurements. The third wafer 134 shown in FIG. 5 includes a secondoutput port 166. A tube 168 is formed around the output port 166.

[0037] The device of FIG. 5 may be operated as follows. Fluid is passedthrough the first input port 144 and is released from the second outputport 166, while the first output port 148 is sealed. This traps bacteriaon filter 160. The second output port 166 is then sealed. A pullingforce is then generated at the first output port 148, which causes thebacteria on filter 160 to flow towards the electrodes 164. During thisoperation, voltages may be applied to the electrodes 164 to divertbacteria into smaller chambers for measurements. Growth media is flowedinto the device, the ports 144, 148, and 166 are then sealed, thebacteria are heated and impedance measurements are taken.

[0038] There are some additional observations to be made with respect tothe device of FIG. 5. The semiconductor surfaces should be oxidized topassivate the silicon surface and to derivatize the surfaces withproteins and bio-molecules as needed. The height-to-width aspect ratioof the pores is preferably as high as possible, for the purpose ofmechanical strength to withstand relatively high-pressure flows. Thismay be achieved by using DRIE semiconductor processing techniques.

[0039] The pore sizes in any of the bacteria trapping filters of theinvention are 0.2 μm or less. The pore sizes of the pre-filters arepreferably in the range of 4-8 μm. This sizing allows bacteria to pass,while trapping other particles, debris, and cells.

[0040]FIG. 6 illustrates an alternate configuration of the device ofFIG. 5. In this embodiment, the electrodes 200 for impedance measurementare immediately adjacent to the second mechanical filter 160. Thus, abacteria transport operation is not required. The surface of the secondmechanical filter 160 may be treated to capture a selected antibody.Fluid is initially pushed through port 144 and is pulled through outputport 166, while output port 148 is sealed. This results in bacteriabeing trapped on filter 160. Output port 166 is then closed and output148 is opened to create a pulling force, which removes the bacteria,except from the selected antibody. Once the unwanted bacteria areremoved, the selected bacteria will remain. Growth media is applied tothe device and a heating operation is commenced. Thereafter, impedancemeasurements are taken.

[0041]FIG. 7 illustrates another integrated filter and growth detector210 configured in accordance with another embodiment of the invention.The detector 210 of FIG. 7 includes a single input port 212 surroundedby a tube 214 and a single output port 216 surrounded by a tube 218. Afirst mechanic filter 220 is formed in a first wafer 222. A secondmechanical filter 224 is formed in a second wafer 226. Electrodes 228are also formed on the second wafer 226. The output port 216 is formedin a third wafer 230.

[0042] Observe that this highly integrated device has only two fluidports. The electrodes 228 can be built on top of the filter 224 andetched such that the metal is aligned to the apertures of the filter. Inthis embodiment, bacteria are captured on the filter 224 andmeasurements are performed without moving the bacteria.

[0043] The device of FIG. 8 generally corresponds to the device of FIG.7, but in this embodiment the electrodes 228 are formed on the sidewallimmediately adjacent to the filter 224. The devices of FIGS. 6-8 may befabricated to include two types of electrodes: electrodes for DEPconcentration and electrodes for impedance measurements. These devicesmay also include separate heating and heating control devices.

[0044]FIG. 9 generally corresponds to the device of FIG. 7, but in thisembodiment a set of first filters 220A, 220B, 220C is provided alongwith a corresponding set of second filters 224A, 224B, 224C. Thisconfiguration facilitates a higher flow rate, but individual chambers240A, 240B, 240C provide electrical viability detection for smallervolumes to provide a low threshold and time to result for detection.With this embodiment, the various chambers 204A, 240B, 240C can bescanned and impedance measurements can be performed sequentially invarious chambers.

[0045]FIG. 10 illustrates still another embodiment of the invention.This embodiment utilizes vertically aligned filters (i.e., filtersaligned vertically or laterally). Observe that prior embodiments of theinvention utilized filters that were horizontally aligned (i.e., alignedin horizontal planes). The device 300 of FIG. 10 includes an input port,a first filter 304 and a second filter 306. In this embodiment,vertically etched pillars form a filter grid or physical barrier.Captured bacteria 308 are routed through a channel 309, which includeselectrodes 312 for dielectrophoresis. The dielectrophoresis electrodes312 route the bacteria to a measurement chamber 316, which includeselectrodes 314 for impedance measurements. The movement of the bacteriais dictated by control of the input port 302, the output port 310 andthe output port 320.

[0046] Fluid is pushed through input 302 and is pulled through output310, while output 320 is sealed. This traps the bacteria 308 on filter306. Voltages applied to the electrodes 312 divert bacteria into thesmaller measurement chamber 316. In the measurement chamber 316,additional electrodes can be used to stop the bacteria migration. Thevalves 318 can then be used to isolate the measurement chamber 316.

[0047] Observe that embodiments of the invention include: (1) afiltration or concentration operation; (2) a DEP concentrationoperation; and (3) a growth (e.g., heating with temperature control) anddetection operation. The filtration operation can be performed in anon-silicon device (e.g., plastic, as shown in FIG. 4). The DEPconcentration operation along with the growth and detection operationsmay be performed on a silicon-based device, also shown in FIG. 4.Alternately, all of these operations may be performed on a silicon-baseddevice, as shown in FIGS. 5-9. As shown in FIG. 10, the DEPconcentration operation may be separate from the growth and detectionoperation. The advantage of this embodiment is that only the measurementchamber 316 needs to be at a micron or nano-scale. For example, in thisembodiment, the electrodes 314 may have a pitch of 10-20 μm and beformed in silicon, while the electrodes 312 may have a pitch of 20-100μm and be fabricated in plastic. This embodiment is cost-effective sinceit reduces the silicon die size.

[0048] Those skilled in the art will appreciate that there are anynumber of process flows that may be utilized in accordance with theinvention. In general, a fluidic sample will be secured and standardoff-chip concentration operations will be performed. These operations,in general, will take approximately 30 minutes. Flow processing andsample concentration is then performed on the chip. This typically takesapproximately 45 minutes. Finally, a growth media is injected into thechip and cell detection is initiated. This process typically takes 2-3hours, a vast improvement over the prior art requirement of many days.

[0049] In order to block bacteria in a relatively large flow, it isdesirable to reduce the conductivity of the flow medium. De-ionized ordistilled water may be used for this purpose. The dielectrophoreticforce on cells is much higher in de-ionized or distilled water than ingrowth media. After cells in a sample have been captured in water, thegrowth media is injected into the chip to replace the water in thechannels, while holding the captured cells using dielectrophoresis.After the water has been flushed out and all the channels are filledwith the growth media, the chip is sealed and the incubation andimpedance measurement process is started. Replacing the water in thechannels by media is essential because water does not provide any of thenutrients the cells need to survive and multiply and withoutmultiplication the metabolic signal is too small to be detected.

[0050] Observe that the highly integrated device of the inventionobviates the prior art use of multiple devices. This eliminates manualprocessing operations, which are time-consuming and error prone. Inaddition, the devices and methods of the invention facilitate automatedmanufacturing processes. Furthermore, the tightly coupled and highlyefficient filtration, concentration, growth and detection operationsreduce processing time. Therefore, the invention can be exploited in avariety of new applications. Major markets include human clinicalapplications, industrial applications, veterinary applications, andhomeland security applications. The human clinical market is huge, withbacterial testing being performed on virtually all patients. Industrialmicrobiological testing is mostly performed in a production environmentin four major segments: pharmaceutical and bio-pharmaceuticalapplications, food applications, environment applications, and beverageapplications. Homeland security is an emerging market that has overlapwith the other markets and will consist of testing of samples from air,water, food supply, and the like for pathogens. The disclosed inventionhas wide applications in all of these markets. A discussion of exemplaryapplications of the invention follows.

[0051] An example where rapid detection of growth of any bacteria iscritical is in biopharmaceutical manufacturing facilities. In thesefacilities, there are many instances where a product is held for manydays for bacterial viability test results or in some cases the productis moved on through additional steps without getting the results. If theresults are negative, then weeks or months of expensive processing iswasted. The reason for this is that these facilities are designed andconstructed to hold large volumes of media, buffer, and product whilethey are stored, waiting for bacterial viability test results. Hence,the rapid bacterial viability test afforded by the present invention canfacilitate a change in the way that pharmaceutical manufacturing isperformed.

[0052] Microbiological control in this segment focuses on themanufacturing environment in order to guarantee control of contaminationrisks and the quality of finished products. Today, the detection and theidentification of bacterial contamination depend largely on conventionalculturing techniques that require several days. Furthermore, today'stracking process still relies mostly on human beings recording resultsin logbooks. It may take up to 10 days to alert the industrial flow toquality control problems.

[0053] In addition, in all biopharmaceutical manufacturing, a regularlyscheduled repair and maintenance shutdown is usually performed twice ayear. For each shutdown, a 7 to 10 day wait period is usually scheduledto obtain the result of bacterial contamination. The fast time to resultsolution of the invention can save up to 15 days per year. This isequivalent to a yearly saving of $7.5 million for a manufacturingfacility requiring $150 million to operate per year.

[0054] The invention can also be used in connection with a variety ofmedical applications. For example, blood and cerebrospinal fluid shouldbe sterile, i.e., have no bacteria. If an infant displays hypothermiaand temperature instability, then a culture of the cerebrospinal fluid,called a spinal tap, is performed. Cerebrospinal fluid bathes the brainand the spinal cord and provides nutrients to these vital organs.Neonatal meningitis, a possible outcome of neonatal sepsis, occurs in2-4 cases per 10,000 live births and significantly contributes to themortality rate in neonatal sepsis; it is responsible for 4% of allneonatal deaths. One milliliter or less of cerebrospinal fluid isextracted and sent for culture. Meningitis can be due to a virus orbacteria. In the case of bacterial infection of the cerebrospinal fluid,early results from a culture can eliminate unneeded medications andtheir side effects when meningitis is not present.

[0055] In the US alone, the incidence of culture-proven sepsis isapproximately 2 in 1000 live births. Approximately 5% of evaluatedneonates have culture-proven sepsis. The early signs of sepsis in anewborn are nonspecific; therefore, many newborns undergo diagnosticstudies and the initiation of treatment before the diagnosis has beendetermined. Medical communities like the American Academy of Pediatrics(AAP), American Academy of Obstetrics and Gynecology (AAOG), and Centersfor Disease Control and Prevention (CDC) have recommended sepsisscreening and/or treatment for various risk factors. Cultures of bloodand body fluids may take several days for the organism to grow and beidentified. Because of this, babies who are at increased risk forsepsis, such as premature or low birth-weight babies may have preventivemedication treatment started as soon as cultures are taken. Because themortality rate of untreated sepsis can be as high as 50%, mostclinicians believe that the hazard of untreated sepsis is too great towait for confirmation by positive cultures; therefore, most cliniciansinitiate treatment while waiting for culture results. The treatments,which in most cases are unnecessary, can have side effects, and also arevery expensive.

[0056] The mortality rate in neonatal sepsis can be as high as 50% forinfants who are not treated. Thus, in this specific and criticalapplication of neonatal blood sepsis and cerebrospinal fluid culture,rapid time to result is specifically of interest. Rapid detection ofgrowth of any microorganisms can have a huge impact on the way neonatalmedicine is practiced in the intensive care unit. Thus, the technologyof the invention facilitates saving lives and reduced treatment costs.

[0057] Another application of the invention is for the identification ofbacterial contamination of transfused blood platelets. Bacterialcontamination of platelets is the leading cause of morbidity andmortality from a transfusion-transmitted infection. It is estimated thatas many as one in 4,000 transfusions leads to a severe septic reactionand as many as one in 12,000 transfusions can lead to death due tobacterial contamination. Platelets are the blood component mostvulnerable to bacterial contamination because they must be stored atroom temperature, which facilitates bacterial growth. Detection iscomplicated by the fact that there are numerous strains of bacteria withvarying growth rates and time needed for some strains to proliferate tothe point where they can be detected. A reliable method must be able todetect the most common and lethal bacteria that contaminate plateletsprior to platelet outdating, which is only five days in the U.S. Thefrequency of bacterial contamination of blood platelets and theincidence of illness and fatalities caused by bacterial contamination,greatly exceed that of viruses. Bacterial contamination can be a problemin most blood products; however, since platelets are stored at roomtemperature they constitute the greatest risk. Thus, the transfusion ofa contaminated platelet product is one of the major causes of death forpatients that have received a transfusion.

[0058] Detection of bacteria in platelets is difficult, mainly due tothe very low initial inoculum present in the product. In addition,platelets may be contaminated with a range of bacteria that will grow atdifferent rates. This makes sampling a major challenge to developers andusers of test systems, and may cause the presence of bacteria in aproduct to be missed due to sampling error. Another challenge is theshort shelf life of platelets (5-7 days). It is therefore very importantto have a rapid and reliable method. Current methods may take daysbefore a positive result is obtained, leaving very little shelf life forthe products. When results can be obtained in a few hours, as is thecase with the present invention, the transfusion can be performed muchearlier from a source of supply, thus reducing the possibility ofadditional contamination.

[0059] As noted earlier, the invention is disclosed in the context ofdetecting bacterial cells, but the disclosed device and the techniquesare equally applicable to other types of cells, such as yeasts, molds,and live mammalian cells.

[0060] The foregoing description, for purposes of explanation, usedspecific nomenclature to provide a thorough understanding of theinvention. However, it will be apparent to one skilled in the art thatspecific details are not required in order to practice the invention.Thus, the foregoing descriptions of specific embodiments of theinvention are presented for purposes of illustration and description.They are not intended to be exhaustive or to limit the invention to theprecise forms disclosed; obviously, many modifications and variationsare possible in view of the above teachings. The embodiments were chosenand described in order to best explain the principles of the inventionand its practical applications, they thereby enable others skilled inthe art to best utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.It is intended that the following claims and their equivalents definethe scope of the invention.

1. A device for rapid concentration and detection of live cells influids, comprising: a filter to capture a cell sample, said filterincluding a physical barrier to isolate said cell sample on said filter;and growth detection circuitry associated with said filter, said growthdetection circuitry electrically measuring a cell growth rate associatedwith said cell sample.
 2. The device of claim 1 wherein said filterincludes a first physical barrier with apertures of a first size and asecond physical barrier with apertures of a second size smaller thansaid first size.
 3. The device of claim 2 wherein said first physicalbarrier apertures have a diameter between approximately 4-8 μm.
 4. Thedevice of claim 2 wherein said second physical barrier apertures have adiameter of approximately 0.2 μm or less.
 5. The device of claim 2wherein said first physical barrier is vertically aligned with saidsecond physical barrier.
 6. The device of claim 2 wherein said firstphysical barrier is horizontally aligned with said second physicalbarrier.
 7. The device of claim 2 wherein said filter includes aplurality of first physical barriers and a plurality of second physicalbarriers.
 8. The device of claim 1 wherein said growth detectioncircuitry includes a heater, a temperature detector, and a sensor. 9.The device of claim 1 wherein said growth detection circuitry includesdielectrophoresis electrodes for concentration of cells.
 10. The deviceof claim 1 further comprising a channel between said filter and saidgrowth detection circuitry.
 11. The device of claim 1 wherein saidgrowth detection circuitry is formed on said filter.
 12. The device ofclaim 1 wherein said growth detection circuitry if formed immediatelyadjacent to said filter.
 13. The device of claim 1 wherein said deviceis formed of silicon and metal on silicon.
 14. The device of claim 1wherein said filter is formed of plastic and said growth detectioncircuitry is formed of silicon, metal on silicon, and glass.
 15. Thedevice of claim 1 wherein said filter is formed of plastic and saidgrowth detection circuitry is formed of silicon, metal on silicon, and aprinted circuit board.
 16. The device of claim 1 includingdielectrophoresis electrodes positioned within a channel adjacent tosaid filter and impedance measurement electrodes positioned within ameasurement chamber.
 17. The device of claim 16 wherein said device isadapted for insertion into a fluidic control device.
 18. The device ofclaim 17 wherein said device is adapted for electrical connection to asignal acquisition and analysis module.
 19. A method of rapidconcentration and detection of cells in fluids, comprising: capturing acell sample within a fluid with a physical barrier; heating said cellsample; and measuring a growth rate signal associated with said cellsample, wherein capturing, heating and measuring are performed on anintegrated device with micron-scale dimensions.
 20. The method of claim19 wherein capturing includes processing said fluid with a firstphysical barrier with apertures of a first size and a second physicalbarrier with apertures of a second size smaller than said first size.21. The method of claim 20 wherein capturing includes processing saidfluid through said first physical barrier, which is vertically alignedwith said second physical barrier.
 22. The method of claim 20 whereincapturing includes processing said fluid through said first physicalbarrier, which is horizontally aligned with said second physicalbarrier.
 23. The method of claim 19 further comprising transporting saidcell sample from said physical barrier to a measurement chamber for saidheating and measuring.
 24. The method of claim 19 further comprisingdelivering said fluid sample to said physical barrier from an externalfluidic control device.
 25. The method of claim 19 further comprisingmeasuring the electrical impedance of said cell sample to detectimpedance changes indicative of the presence of cell growth.
 26. Themethod of claim 19 further comprising providing growth media to saidcell sample.
 27. The method of claim 19 wherein heating includesmeasuring the temperature of said device, heating said device to aselected temperature, and maintaining said device at said selectedtemperature.